Mainz hammered a second-stringBorussia Dortmund 3-0 on Saturday to haul themselves out of the Bundesliga's
bottom three, as Cologne came back to beat Union Berlin in a day of much importance for the relegation battle.Sitting in the relegation playoff spot at kick-off, Mainz stunned thevisitors by racing into a three-goal lead inside just 23 minutes. Leandro Barreiro opened the scoring on 12 minutes, before Lee Jae-sunggrabbed two goals in three minutes as the hosts tore into a much-changed Dortmund side.

Mainz, who are now eight games unbeaten since losing 8-1 to Bayern Munich in
March, realistically need just a point from their final game of the season at
Wolfsburg to secure another season in the German top flight.

With Dortmund's Champions League qualification for next season now
guaranteed, and a Champions League final against Real Madrid on the horizon,
Dortmund coach Edin Terzic rang the changes.

Defender Nico Schlotterbeck was the only starter from the team that won in
Paris on Tuesday and though Jadon Sancho, Ian Maatsen and Julian Brandt came
off the bench at half-time, they could not turn the tide.

Terzic defended the decision to make sweeping changes to Dortmund's XI,
insisting his choice of line-up was not unlike the team that beat Augsburg 5-
1 last weekend, with three changes from that side.

"We set up the team similarly to what we did last week," Terzic told Sky
Sport Germany.

"We had a similar formation, only this time we were always inferior in the
duels. Mainz punished the mistakes we made in the first half with ice-cold
precision. That's why it is a deserved defeat."

Dortmund now sit four points behind fourth-place RB Leipzig, who drew 1-1
with Werder Bremen earlier on Saturday.

But one spot behind Dortmund in sixth, Eintracht Frankfurt are a distance
adrift of Terzic's side, and drew 1-1 at Borussia Moenchengladbach in their
penultimate match of the season.

At the other end of the table, Mainz's victory leaves Union Berlin, who
squandered a 2-0 lead at Cologne earlier in the day to lose 3-2, languishing
in the thick of the relegation fight.

- 'Hugely important victory' -

Cologne teenager Damion Downs came off the bench to score a 92nd-minute
winner, keeping their hopes of a miraculous great escape alive.

Union had raced into a 2-0 lead inside 19 minutes with Robin Knoche's
thumping header and Kevin Volland's penalty putting the Berliners in complete
control.

A Florian Kainz penalty shortly before half-time gave Cologne hope but
Union's lead remained intact until the 87th minute, when Cologne staged a
stunning turnaround.

Steffen Tigges scored from close range to make it 2-2 and, with Union still
reeling, 19-year-old substitute Downs converted Linton Maina's cross to raise
the roof and give his side an invaluable win.

"We're overjoyed," Cologne captain Kainz told Sky Sport Germany.

"It's nerve-wracking to play like that, when you absolutely have to win the
game. To turn it around, it was a hugely important victory. Unbelievable."

But Mainz's victory means the best Cologne can hope for on the final day is
to secure a relegation play-off place at Union's expense.

Union, who started the season in the Champions League but are now on a
miserable run of two points from their last seven games, face a tricky season
finale against Freiburg -- who remained in the last European spot after
drawing 1-1 against Heidenheim on Saturday.

Cologne travel to Heidenheim on the last day needing to muster another
victory and hope that Freiburg win in Berlin.

Goal difference and goals scored would also come into play in this scenario,
with Cologne needing a four-goal swing to finish above Union.

One of Germany's 'yo-yo clubs', Cologne are looking to avoid a record seventh
relegation since their first in 1998.

Bochum, who host champions Bayer Leverkusen on Sunday and travel to Werder
Bremen on the final day, need a point from one of those games to ensure their
Bundesliga survival.